Antioxidant



' is reacted i N' disubs'tituted material.-

Patented May 16, 1.944

United States Rubber N. Y., a corporation of y, New York, New Jersey No Drawing. Application January 13, 1943, Serial No. 472,273

15 Claims.

This invention relates to improvements in antioxidants, and more particularly for preserving rubber and similar oxidizable materials.

This application is a continuation-in-part of my application Serial No. 374,478, filed January 15, 1941.

An object of the invention is to provide a new class of anti-oxidants or age resisters for unsaturated organic substances which tend to deteriorate by absorption of oxygen from the air, for example, goods of rubber or allied gums, unsaturated fatty oils such as unsaturated vegetable oils, essential oils, petroleum oils and their derivatives such as gasolines, soaps, aldehydes, synthetic resins, turpentine, paints, and the like. A further and important object of this invention is to provide chemicals which additionally act as flex improvers or flex cracking agents for vulcanized rubber such as tire treads,.which undergo repeated strain during use. Further objects will be apparent from the following description.

According to the invention, the organic substance is treated with an anti-oxidant of the general formula where R represents an aromatic group such as phenyl, naphthyl (or homolog or analog thereof), which 'may contain further substituents; R. is an arylene nucleus; A is a hydroxy alkyl group; and is hydrogen or a hydroxy alkyl group.

The materials may be prepared reacting a diaryl arylene dianiine with an' alkyleiie oxide (CnHimQ) or substituted alkyleiie oxide. enabling '''the carbon chain, besides being linked to it 1137- droxy gi'o llb, to be also iii the final compounds by a discrete carbon atom to an original.

secondary amin nitrogen atom; represents an integer of at least diaryl a ylene dia U by passing the a'lkyle'n'e' oxide into" a solution of the diary! ar'ylene diafiiin'e iii an lliert solvent, e.

peratui'fe's of which a range of about C. to

tion may be carried out by slowly passing the alkylene oxide into the heated dieiiiiine under atinospheric r under uper atmosp eric pressures. It is desirable that the slamme- B stirred so as tocontinually expose fresh alkylation and to minimize" The reaction products 2.- lii' this reactioii the. he and tlie alkyleiie oxide v (h xane,- benzene, etc; or intotne' molten diaryl arylene diamine'. In general. it is" surfaces tor hydrbxy the formation or N4 tion, they may be neutralized with alkali to remove the acid.

It is relatively easy to separate unreacted oxide since this material is very volatile and the unreacted diamine can be substantially separated by extracting the crude product with an organic solvent such as alcohol or benzene in which the diary] arylene diamine is relatively insoluble. To isolate the monohydroxy alkylated derivative is more difllcult as this class of materials is characterized as low melting oils quite soluble in the usual organic solvents. The di-hydroxy alkylated material can be isolated by a series of fractional crystallizations since these materials tend to be more crystallized than the mono-hydroxy alkylated bodies. To prepare the di-hydroxy alkylated derivatives, the preferred procedure is to use a large excess of oxide and to repeat the hydroxy alkylation if necessary.

The composition of the product, produced by the aforesaid reaction, is controlled by the amount of the alkylene oxide that is caused to react with the diaryl arylene diamine. To prepare a product consisting substantially of mono-hydroxy alkylated material between 1 and 2 mols of the oxide, more specifically about 1% mols of the oxide, are caused to react with 1 mol of the diamine. To prepare a di-hydroxy alkylated material, at least 2 and preferably 3 or 4 mols of alkylene oxide per mol of diamine are employed in the reaction. V In the reaction between the oxide and the diamine a catalyst usually is not necessary, especially in. working with ethylene oxide, propylene acid, ferrous chloride,-- ferrous iodide;

, chloride, sulfuric acid; and phosphoric acid.

. nece sar to effect this reaction at elevated tem-' may be used as'prepared, or used in more purified I m b d m tss w ed 9 el e the mono-'hydroxy alkylated body; siiic unsymmetrical; message is low me tin and usually a viscous liquid,- but in general; a prod-1 u'ct consisting Ora prepoiiderant mo -hydroxy alkylated materi l iii :1 be are pared by passing in an allrylene oxide to the diaryl arylene qialim'i e until tneurfireactee an amine content drops to a low level such about %orles's. I V

a The mono-hydroxy alkylate'd diaryl-armene diamine may be produced in more purified term by synthesis from a diarylamirie'. I mono-N+(b-hydroxy' ethyl) N,N'-diplierlyl b phenylene diaminej cal-Nae prepared by heating diphenylamine' with ethylene oxide to form For example,

with alkylene oxides, such as u aniline, which provide poor, resistancev ageing, and reduced flexing life of the rubber conthem-the present chemicals provide for the reaction pf'oduct of 1 /4 Diphenyl p-phenylene N-hydroxy alkyl diphenylamine. This product is then nitrosated to form the para-nitroso body (Cloez, Comptes Rendus 124, 898) which can be reduced to the amine by treatment with excess stannous chloride. The acetyl derivative of the amine may be condensed with iodobenzene (Wieland, Ber., 41, 3493) and the resulting acetyl derivative hydrolyzed with alcoholic potassium hydroxide to form the final product. In the event that a diarylamine having both para positions blocked is used as a starting material, the nitrowas prepared by The following examples in which the parts are by weight, are given to illustrate the invention and are not to be considered as limiting thereof:

EXAMPLE 1.-'Preparation of N -(b-hydra:y ethyl) N,N'-diphenyl p-phenylene diamine N-(b-hydroxy ethyl) diphenylamine, a yellow oil B. R. 155-160 C. at 1 mm. mercury pressure heating 33.8 gr. diphenylamine and 8.8 gr. ethylene oxide hours at 240-250 C.

This material was acetylated by refluxing 10': gr.

sation will form an ortho-nitroso substituted amine which will ultimatelylead to an orthophenylene diamine derivative. unsymmetrical amines as starting materials, it is advisable to first have a nitro group presenti'n In the cases of acetyl derivative distilled 140-145" [and was converted treating 79 gr. of it the desired orientation before the reaction with the alkylene oxide. The nitro group is then reduced to an amine which is converted to the sec ondary amine.

Unlike the reaction products of primary amines beta-hydroxy ethyl to heat taining rubber products having markedly and unexpectedly superior properties in this respect.

Another advantage of the present anti-oxidants is that they are substantially non-blooming'in rubber, which is a characteristic absent-from diaryl arylene diamines such as NIP-diphenyl p-phenylene diamine. If."

In addition to being more soluble in rubbe'ithan the diaryl arylene diamines, the present reaction roducts are soluble in ketone-amine condensation products to produce a mixed anti-oxidant which is superior to that referred to in Howland U. S. Patent No. 2,183,567. For example, in the case Of diphenyl p-phenylene diamine and acetone-diphenylamine condensate, mately 5% of the diamine can be dissolved, while mols of ethylene oxide with 1 mol or p-phenylene diamine is soluble to a greater extent with the acetonediphenylamine condensate. The reaction prod-- uct of'the oxide and a diaryl arylene diamine is also more soluble, than the diphenyl'phenylene diamine, in 2,2,4-trimethyl 1,2-dihydroquinoline.

Exemplary'of the oxides which may be reacted withany of the diamines as disclosed are the following:

, Ethylene oxide "Ditolyljp-phenylene diamine Y Di(peanisyl p-phenylene) diamine Di(p-xenyl*p-phenylene) diamine Di-beta-naphthyl p-phenylene diamine Di-alpha-naphthyl p-phenylenediamine Diphenyl l-'-4-naphthalene diamine Di(p-chloro phenyl), p-phenylehe diamine Di(p-tert butyl phenyl) p-phenylene diamine Diphenyl p-tolylene diamine approxi- T group which is the reason of it with 56 gr. acetic anhydride 1 hour. The C. at 1-2 mm. to the p-nitroso derivative by in 250 cc.-alcohol and 65 cc. concentrated hydrochloric acid at 5 C. with 17.3

7 gr. sodium nitrite in '75 cc. water after which the p-nitroso derivative was reduced with 169 gr. stannous chloride dihydrate in 125 cc. concentrated hydrochloric acid. The reduced solution was made alkaline and the amine separated by extraction. It boiled 110-205 C. at 1 mm. The acid reduction partially hydrolyzed the acetyl for. the C. boiling range of the reduced product; however, the acetyl group was reintroduced in the next step.

The reduced amine B. R. PTO-205 C. at 1 mm. v 50 gr.) was allowed to stand minutes with cc. acetic anhydride and 40 cc. acetic acid,

A yield of 32.5 gr. crystalline acetylderivative' was obtained. This 32.5 gr.

was refluxed 25 hours in 100 cc. methyl hexyl carbinol with 21.2 gr. iodo-benzene, 19.4 gr. anhydrous potassium car- ,bonate and /2 gr. copper powder. Aiterremoving the methyl hexyl carbinol by steam distillation and the inorganic chemicals by extraction with benzene and removing the benzene by evaporation with alcohol the residue was by- The product distilled wdrclyzedvwith 10 gr. sodium hydroxide in 10 cc.

water and-50 cc. alcohol by refluxing 5 hours.

Fraction Boiling range 186-242 C. at 4 min. i1 MO-260 .athnm. 270280 at 4 mm.

"Freetibiiiii nab i mx ethyl) N,N' diphenyl p-Dhenylene diamine In the subsequent rubber tests it is identiiieda chemical I.

Diphenyl p-phenylene diamine (26 gr.) (0.1 mol) and 15 cc. (13.2 gr.; 0.3 mol) ethylene oxide were heated in'av sealed tube overnight" at C. and then overnight at 250 C. The contents of the tube were dissolved in hot benzene. On cooling, the desired product crystallized out. Recrystallized from dilute alcohol. Yield 17 grams. Pure white crystals, melting point134 C. In the subsequent rubber test examples it is identified as Chemical II.

ExA rLa 3.--Preparatioh of N-(b-hydromy ethyl) MA N-diphenyl p-phenylene diamine from ethylene oxide and diphenyl p-phenylene diamine In a 5 gallon steel autoclave equipped with a stirrer,'22 pounds, 14 ounces (1 mol) of technical diphenyl p-phenylene diamine was heated to C. Over an 8 hour period, 4'pounds, 10 ounces (1.24 mol) of ethylene oxide was passed in. Heating andstirring were continued 1 hour and the contents discharged. The product is a heavy rubber tests.

EXAMPLE 4 Ethylene oxide (6 -cc.) was condensed in a' test tube in an acetone-dry ice bath and the .tube closed so as to eflect a thin seal. N,N-diphenyi p-phenylene diamine (26 grams) was placed in a Carius tube along .with a small piece of steel and the tube of ethylene oxide. After the Carius tube had been scaled it was shaken until the steel broke the test tube containing the ethylene oxide. The contents were then heated overnight at 175 C. and the product was purified by dissolving in acetone, filtering and removing the solvent by vacuum distillation. The product, a thick oil analyzed 8.64 percent nitrogen. It is identified, as chemical IV in the rubber tests. It consists of a mixture of N-ib-hydro'xy ethyl) N,N'-diphenyl p-phenylene diamine and NM di-(b-hydroxy ethyl) N,N'-diphenyl p-phenylene diamine.

EXAMPLE @iphenyl pphenylene diamine gr.) and 12 gr. isobutylene oxide were autoclaved '72 hours at 200 C. The product on'va'cuum distillation gave two fractions:

Fraction 1, boiling range 225-250 C. at 3 mm. Fraction II, boiling range 260-265 C. at3 mm.

The latter, a dark red oil, consists substantially of N-(b-hydroxy isobutyl) N,N'-diphenyl pphenylene diamine. It analyzed 8.8% nitrogen.

Theory 8.45% nitrogen. According to this analysis the distillate consisted of 15% diphenyl pphenylene diamine and 85% N-(b-hydroxy isobutyl) N,N'-dipheny1 p-phenylene diamine. It is identified as chemical V in the rubber tests.

'ExAmrLa- 6 Diphenyl p-phenylene diamine (26 gr.) was autoclaved overnight at 200 C. with 5.8 gr. propylene oxide and 0.1 gr. iodine as catalyst. The product was dissolved in benzene and the solution washed with dilute sodium hydroxide. On vacuum distillation a thick red oilboiling range 250-275 C. at 5 mm.'was obtained. It is identifled as chemical VI in the rubber tests. I

The following examples refer to rubber testing data:

EXAMPLE 7 .--Test of chemical I of Example 1 and test of chemical II of Example 2 Master batch used:

Cures were made for 30, 45, 60; and '75 minutes at 30 pounds per square inch steam pressure.

0 Mercaptobenzotliia z ole.

UNAGED TENSILES (IN POUNDS masculine mom Elon- Cum gation A B 30 minutes at 45 lbs. per 1 5' v m Break 3,050-685 3, 710 660 3320 080 45 minutes at 45 lbs. per 2 .i;% 2%- Break 3.570 652 3,840'-602 seed-s51 minutes at 45 lbs. per 233 610 g lgg in Break 3, 640 646 3, 670 595 3, 110 655 minutes at 45 lbs. per Q 553 Q13 Break 3, 630 625 arsed-55s aszo'soa AGED as nouns UNDER 30o POUNDS OXYGEN AT 10" o.

Cure 25,; A B C 30 minutes at 45 lbs. per g $3 1 $8 in Break "330 145 2, 590 600 1490 613 45 minutes at 45 lbs. per ggg 350 2,

Break "time 15516 455 aasd-sa'l 60 minutes at 45 lbs. per Q33 Break stasis 2.32am 75 minutes at 45 lbs. per 3 Breals time rim UNAGED DUMBBELL FLEXINGS 'Ex rrs 8.Test of chemical m of Example 3 Anti-oxidant Control stock Copolymer... Antioxidant Sulfur Coal tar softener. Carb -Zinc oxide...

The stocks were cured 30,45, and 60 minutes 1 at 45 pounds per square inch-steam pressure.

TENSILES (AFTER AGEING) Elon- Am cum gation m oxidant I 300 390 410 30mlnutes at 4 5 lbs. per sq. in. 500 1,000 1,180 Break 1, 480640 2, 240-773 I 300 50 45 minutes at 45 lbs. per sq. m 500 1,590 l. 640 Break 1, 990-560 2, 800-673 300 800 60minutes at 45lbs. persq. in 500.-. 2,050 Break 850-486 2. 410-565 EXAMPLE 9.-Test of chemical IV of Eaample! This material was tested in a typical tread stock of natural rubber, the 'parts being by weight: v Smoked sheet -Q 100 Carbon black 45 Zinc soap of cocoanut oil acids 3.5 Pine tar 3.5 Zinc oxide 5.0 Sulfur 3.0 Mercaptobenzothiazole (accelerator) 1.0

Chemical Control 1v Kilocycles to end point 1, 949 3, 109

Exnmrrr: 10.--Test of chemical V of Example 5 and test of chemical VI of Example 6 These materials were tested in the same tread stock as in the previous example using 1 part per 100 parts rubber. Theyv too imparted improved resistance to ageing in oxygen 96 hours under under 300 pounds per square inch pressure at 70 F. and 96 hours at 212 F.

UNAGED DUMB-BELL FLEXINGS Control Chenille!!! Chevniical- Kllocycles to end point l, 906 4, 419 4. 510

The anti-oxidant may be incorporated in any type of rubber composition, such as those used for automobile'tires and tubes, hose, belting, sheet and thread rubber, rubberized fabrics, molded goods, boots and shoes, etc., whether vulcanized in a mold, in open steam, in hot air, or in the cold by the.so-called acid process. The proportion of the anti-oxidant may vary from about 0.1% to 5%, although either smaller or greater proportions may be found useful. If the material to which it is added is a liquid such as rubber'cement or an oil, the anti-oxidant may be dissolved therein in a suitable mall proportion. The anti-oxidant may be incorporated into solid substances by milling or mastication and prepared for tions either in powder, paste or solution form, or applied in such forms for incorporation by diffusion, to the surfaces of vulcanized or unvulcanized rubber goods.

The term a rubber is employed in the claims to define a vulcanizable plastic material which possesses high-extensibility under load coupled with the property of flexibly retracting to approximately its original size and shape after the load is removed and includes india rubber, balata, gutta percha, and other natural rubbers as well as synthetic 'vulcanizable products such as p lychloroprene, olefin polysulfides, butadiene polymers, and modified butadiene polymers (Buna N and Buna S) and the like, which have a flexibility and elasticity similar to rubber, and reclaims and latices of such materials, which deincorporation into dispersions or soluteriorate upon ageing, whether or not admixed with fillers, pigments, accelerating agents, softeners, etc.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. A method of preserving organic substances which tend to deteriorate by absorption of oxygen fromethe air which comprises incorporating therein a compound of the general formula x A R-l l'-R'll-R where R represents an aromatic nucleus; R is an arylene nucleus A is a hydroxy-alkylgroup having at least two carbon atoms in the chain; and X is a radical selected from the class consist ng of hydrogen, and a hydroxy-alkyl group.

2. A method of preserving organic substances which tend todeteriorate by absorption of oxygen from the air which comprises incorporating therein a compound of the general formula R'l I-R'1 I-R where R represents an aromatic nucleus; R is an arylene nucleus; and A is a hydroxy-alkyl group having at least two carbon atoms in the chain.

3. A method of preserving organic substances which tend to deteriorate by absorption of oxygen from the air which comprises incorporating therein a compound having the general formula C nHhOH c.n,..on H

I O Q N N where n is an integer of at least 2.

5. A method of preserving organic substances which tend to deteriorate by absorption of oxygen from the air which comprises incorporating v therein a compound having the general formula ornon'lon i I where X is a radical selected from the class con sisting of hydrogen and CHzCHzOH.

6. A method of preserving organic substances which tend to deteriorate by absorption of oxygen from the air which comprises incorporating therein a compound having the general formula CHzCHzOH oxygen from the air which comprises incorporating therein an N,N'-diaryl p-arylene, diamine'in which an original secondary amino nitrogen atom is directly attached to a carbon atom of a saturated hydrocarbon chain, another of' the carbon atoms of said chain being directly attached to a hydroxy radical.

8. A method -of preserving a rubber composition which comprises-incorporating therein an N,N-diaryl p-arylene diamine in which an original secondary amino nitrogen atom is directly attached to a carbon atom of a saturated hydrocarbon chain, another of the carbon atoms of said chain being directly attached to a hydroxy radical.

9. A method of preserving organic substances which tend to deteriorate by absorption of oxygen from the air which comprises incorporating therein an N,N'-diary1 p-arylene diamine in which an original secondary amino nitrogen atom is directly attached to a carbon atom of an 'alkanol group containing at least two carbon atoms in the chain.

10. A method of preserving a rubber composition which comprises incorporating therein an N,N'-diaryl p-arylene diamine in which an original secondary amino nitrogen atom is directly attached to a carbon atom of an alkanol group containing at least two carbon atoms in the chain.

11. An organic substance which tends to deteriorate by absorption of oxygen from the air containing a compound as set forth in claim 1.

12. An organic substance which tends to deteriorate by absorption of oxygen from the air containing a compound as set forth in claim 3.

13. A rubber composition containing a compound as set forth in claim 3.

14. An organic substance which tends to deteriorate by absorption of oxygen from the air containing an N,N'-diaryl p-arylene diamine in which an original secondary amino nitrogen atom is directly attached, to a carbon atom of a saturated hydrocarbon chain, another of the carbon atoms of said chain being directly attached to a hydroxy radical.

15. A rubber composition containing an N,N'- diaryl p-arylene diami'ne in which an original secondary amino nitrogen atom is directly attached to a carbon atom of an alkanol group containing at least two carbon atoms in the 

